1. Field of the Invention
The present invention relates to a fingerprint input apparatus for identifying an individual. More specifically, the present invention relates to a fingerprint input apparatus which includes a switch for detecting that a finger is put on a sensor element which reads a fingerprint, on an opposite surface to a surface on which the sensor element is provided, across a housing.
2. Description of the Related Art
Conventionally, a fingerprint input apparatus is normally used while being connected to another apparatus such as a computer. In order to prevent the computer from being operated by unspecific persons, it is necessary to check whether a user who is to operate the computer is a person permitted to operate the computer. To this end, the fingerprint input apparatus is used. The fingerprint input apparatus authenticates an operator by acquiring a fingerprint of the operator and comparing the fingerprint of the operator with a fingerprint of an operation-permitted person that is registered in advance.
As can be understood from the above, the fingerprint input apparatus is not an apparatus required to constantly operate. Due to this, with a view of reducing power consumption, it is desirable that the fingerprint input apparatus operates only when a fingerprint is input. In addition, it is necessary to ensure that the apparatus operates when the fingerprint is input. It is, therefore, necessary to detect that the fingerprint is input by some means and to start a predetermined operation in response to a detection signal.
If the fingerprint input apparatus does not include a special mechanism of generating a fingerprint input detection signal, it is necessary to always activate the apparatus, continuously acquire images from a sensor element, and determine whether each obtained image is a fingerprint image by means of software. To do so, the fingerprint input apparatus requires a storage capacity and a processing capacity for this software, and consumes a power, accordingly.
Examples of providing the fingerprint input apparatus with a switch for outputting the detection signal includes following Japanese Patent Application Laid-Open No. 10-240900 (JP-A). According to JP-A 10-240900, a read start switch is provided separately from an apparatus main body. However, the technique disclosed in JP-A 10-240900 is on the premise that an operator who takes fingerprints operates the switch. In addition, JP-A 10-240900 fails to describe providing optimum arrangement in which a person the fingerprint of which is taken operates the apparatus by a fingerprint detection target hand. Further, the example of JP-A 10-240900 is limited to the fingerprint input apparatus of such a type as to optically read the fingerprint.
The fingerprint input apparatus needs to acquire an image of a quality suited for an image processing performed for fingerprint authentication. The quality of the image depends on a depression pressure applied when a finger is put on the sensor element. To acquire the high quality image, therefore, it is necessary to put the finger on the sensor element with an appropriate depression pressure.
The apparatus disclosed in the JP-A 10-240900 does not include means for notifying the user whether the depression pressure is appropriate.
If the fingerprint input apparatus does not include the means for notifying the user whether the depression pressure is appropriate, the user inputs the fingerprint at an entirely arbitrary depression pressure. Due to this, the fingerprint input apparatus needs to install a software for determining the quality of the acquired image. The software is required to determine the quality of the image, and to reacquire an image if the quality does not reach a predetermined quality.
As can be seen, the fingerprint input apparatus which does not include the means for notifying the user whether the depression pressure is appropriate is required to perform a complicated software processing. As a result, a storage capacity and a processing amount of the software are disadvantageously increased, thereby disadvantageously increasing power consumption.
Considering the disadvantages, a fingerprint input apparatus which includes a switch for notifying a user of an appropriate finger depression pressure is known as disclosed in Japanese Patent Application Laid-Open No. 2000-57328 (JP-A).
FIG. 7 is a cross-sectional view of the fingerprint input apparatus disclosed in JP-A 2000-57328.
In FIG. 7, reference 11 represents a sensor element, 12 represents an upper surface of the sensor element 11, 13 represents a plate spring, and 14 represents a switch.
The fingerprint input apparatus shown in FIG. 7 includes the switch 14 for notifying the user of the appropriate depression pressure and the sensor element 11 which generates a fingerprint input detection signal. In the example of FIG. 7, the sensor element 11 itself is held by the plate spring 13 or the like. When the user puts a finger on the sensor element 11 and depresses the sensor element 11, the switch 14 arranged on a rear surface of the sensor element 11 is depressed, thereby generating a detection signal and activating the fingerprint input apparatus. The appropriate depression pressure is notified to the user by a repulsive force of the plate spring or by giving a feel that the switch is depressed.
The conventional technique disclosed in JP-A 2000-57328, however, requires the spring for holding the sensor element. The use of the spring causes the following two disadvantages.
First, the number of components increases. If the number of components increases, a cost is pushed up and a reduction in size and weight of the apparatus cannot be realized.
Second, a mechanism for fixing the spring to the sensor element and the housing is required. This mechanism is undesirable since the configuration of the apparatus is complicated.
In addition, the following disadvantages resulting from the configuration of the apparatus in which the sensor element itself moves occur.
First, since the apparatus is configured so that the sensor element moves and depresses the switch, a clearance is necessary between the rear surface of the sensor element and the switch. This disadvantageously hinders a reduction in the size of the apparatus.
Second, a mechanism such as a hinge or a guide for enabling the sensor element to properly move is required, thereby disadvantageously, undesirably complicating the configuration of the apparatus.
Third, a movable section such as the hinge tends to cause a malfunction, thereby disadvantageously deteriorating maintainability and reliability of the apparatus.
Fourth, since the fingerprint sensor element which needs to be exposed to an external world so as to contact with the finger is movable, it is difficult to realize the configuration with high waterproofness and high dustproofness.